Formation potential and source contribution of secondary organic aerosol from volatile organic compounds

Abstract

Secondary organic aerosol (SOA), a key constituent of fine particulate matter, can be formed through the oxidation of volatile organic compounds (VOCs). However, information on its relevant emission sources remains limited in many cities, especially concerning different types of land use. In this study, VOC concentration in Bangkok Metropolitan Region (BMR), Thailand, was continuously collected for 24 h by 6-L evacuated canister and analyzed by gas chromatography/mass spectrophotometry following USEPA TO15, and the formation of SOA was evaluated through the comprehensive direct measurements and speciation of ambient VOCs. Finally, source contribution of VOCs to SOA formation was characterized using the Positive Matrix Factorization (PMF) model. The results revealed the abundant group of VOCs species in the overall BMR was oxygenated VOCs, accounting for 49.97–57.37%. The SOA formation potential (SOAP) ranged from 1,134.33 to 3,143.74 μg m−3. The VOC species contributing to the highest SOAP was toluene. Results from the PMF model revealed the dominant emission source of VOCs that greatly contributed to SOA was vehicle exhaust emission. Industrial combustion was the main source of VOC emission contributing to SOA in industrial areas. Sources of fuel evaporation, biomass burning, and cooking were also found in the study areas but in small quantities. The results of this study elucidated that different emission sources of VOCs contribute to SOA with respect to different types of land use. Findings of this study highlight the necessity to identify the contribution of potential emission sources of SOA precursors to effectively manage urban air pollution.